Hi @lmaher ,
Thank you for getting in touch. Can you let me know if you only have a tax registration in the Republic of Ireland, or if you have one in the United Kingdom as well? If you have both, the UK tax registration takes precedences and the UK VAT rate will be charged when selling products to Northern Ireland. This is outlined in this Help Center article:
Whether or not UK or EU VAT is charged when selling from an EU country to Northern Ireland should primarily depend on which tax registrations the business holds. If you do not hold a UK VAT registration but are still seeing the UK VAT rate of 20% when selling to Northern Ireland, please let me know and I’ll take a further look into why this might be happening.